Quantitative Mass Spectrometry incorporates collaborative projects in which the Mass Spectrometry Group provides quantitative information about, typically, small molecules by GCMS, LCMS and LCMSMS or a combination. An example of the types of projects this includes is the isoprostane analyses undertaken as part of the NIEHS led study of biomarkers of oxidative stress. We currently have several major collaborations underway. 1) with the Zeldin Lab quantitating arachidonic acid metabolites that are relevant to inflammatory, vasodilatory, endothelial protective and post-ischemic cardioprotective effects. 2) a collaboration with James Mohler/Mark Titus on a Program Project (UNC/Roswell Cancer Institute) on Interference with the Androgen Receptor and its Ligands in Recurrent Prostate Cancer. As part of this study, we have: a) successfully developed an LC/MS/MS protocol for the analysis of T, DHT, dihydroepiandrosterone, androsterone, 5-androstenediol, and androstenedione at the low femtomolar level (0.15 to 9 fM except for the saturated diol) based on the use of atmospheric pressure photoionization (APPI). Enhanced sensitivity for non-conjugated ketosteroids, such as DHT, was achieved via the monitoring of an (M+14)+ ion arising from alkylation of the analyte by the methanolic solvent used in APPI. (Patent application pending;b)applied our APPI assay to the quantitation of these analytes in diverse CaP cell lines. In these experiments, either T in combination with inhibitor or 3-androstandediol, was added to the cell lines and DHT levels were measured after 48 hrs incubation. 3) Investigating enzymatic vs. non-enzymatic pathways in the formation of F2alpha isoprostane in biological systems to identify the extent, if any, of enzymatic formation.